T-type Ca2+ channels are often aberrantly expressed in different human cancers and participate in the regulation of cell cycle progression, proliferation and death. Methods: RT-PCR, Q-PCR, western blotting and whole-cell patch-clamp recording were employed to assess the expression of T-type Ca2+ channels in leukemia cell lines. The function of T-type Ca2+ channels in leukemia cell growth and the possible mechanism of the effect of T-type Ca2+ channel antagonists on cell proliferation and apoptosis were examined in T-lymphoma cell lines. We show that leukemia cell lines exhibited reduced cell growth when treated with T-type Ca2+ channel inhibitors, mibefradil and NNC-55-0396 in a concentration-dependent manner. Mechanistically, these inhibitors played a dual role on cell viability: (i) blunting proliferation, through a halt in the progression to the G1-S phase; and (ii) promoting cell apoptosis, partially dependent on the endoplasmic reticulum Ca2+ release. In addition, we observed a reduced phosphorylation of ERK1/2 in MOLT-4 cells in response to mibefradil and NNC-55-0396 treatment. These results indicate that mibefradil and NNC-55-0396 regulate proliferation and apoptosis in T-type Ca2+ channel expressing leukemia cell lines and suggest a potential therapeutic target for leukemia.

Purpose: Although tyrosine kinase inhibitors (TKI) such as imatinib provide an effective treatment against Bcr-Abl kinase activity in the mature cells of patients with chronic myelogenous leukemia (CML), TKIs probably cannot eradicate the leukemia stem cell (LSC) population. Therefore, alternative therapies are required to target both mature CML cells with wild-type (WT) or mutant Bcr-Abl and LSCs. To investigate the effect of C086, a derivative of curcumin, on imatinib-resistant cells, we explored its underlying mechanisms of Bcr-Abl kinase and heat shock protein 90 (Hsp90) function inhibition. Experimental Design: Biochemical assays were used to test ABL kinase activity; fluorescence measurements using recombinant NHsp90, Hsp90 ATPase assay, immunoprecipitation, and immunoblotting were applied to examine Hsp90 function. Colony-forming unit, long-term culture-initiating cells (LTC-IC), and flow cytometry were used to test CML progenitor and stem cells. Results: Biochemical assays with purified recombinant Abl kinase confirmed that C086 can directly inhibit the kinase activity of Abl, including WT and the Q252H, Y253F, and T315I mutations. Furthermore, we identified C086 as a novel Hsp90 inhibitor with the capacity to disrupt the Hsp90 chaperone function in CML cells. Consequently, it inhibited the growth of both imatinib-sensitive and -resistant CML cells. Interestingly, C086 has the capacity to inhibit LTC-ICs and to induce apoptosis in both CD34+CD38+ and CD34+CD38− cells in vitro. Moreover, C086 could decrease the number of CD45+, CD45+CD34+CD38+, and CD45+CD34+CD38− cells in CML NOD-SCID mice. Conclusions: Dual suppression of Abl kinase activity and Hsp90 chaperone function by C086 provides a new therapeutic strategy for treating Bcr-Abl–induced leukemia resistant to TKIs. Clin Cancer Res; 21(4); 833–43. ©2014 AACR.

A facile and green method has been demonstrated to synthesize ultrasmall tungsten oxide quantum dots (WO_x QDs). The water-soluble WO_x QDs present high luminescence stability, strong peroxidase-like activity, and excellent electrochemiluminescence properties. This work provides an eco-friendly strategy to prepare multifunctional WO_x QDs, and opens the door for bioapplications of the WO_x QDs.